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Reaching the Age of Adolescence - Secondary Sexual Characteristics

Grade 8CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Secondary Sexual Characteristics: These are physical features that appear during puberty which help distinguish a male from a female. They are controlled by hormones produced by the endocrine system.

Role of Hormones: The changes at adolescence are controlled by chemical substances called hormones. The male hormone TestosteroneTestosterone is secreted by the testes, and the female hormone EstrogenEstrogen is secreted by the ovaries.

Changes in Males: These include the growth of facial hair (beard and moustaches), deepening of the voice, and the development of the LarynxLarynx (Adam's Apple).

Changes in Females: These include the development of mammary glands (breasts), broadening of the pelvic region (hips), and the start of the menstrual cycle.

Endocrine Glands: The Pituitary glandPituitary\ gland (master gland) secretes hormones that stimulate the testes and ovaries to produce TestosteroneTestosterone and EstrogenEstrogen respectively.

Sweat and Sebaceous Glands: Increased activity of these glands during adolescence often leads to the occurrence of acne and pimples in young people.

📐Formulae

Calculation for Full Height (cm)=Present Height (cm)% of full height at this age×100\text{Calculation for Full Height (cm)} = \frac{\text{Present Height (cm)}}{\% \text{ of full height at this age}} \times 100

💡Examples

Problem 1:

A boy is 99 years old and is 120 cm120\text{ cm} tall. At the end of the growth period, he is expected to be 75%75\% of his full height. Calculate his probable full height.

Solution:

Probable Full Height=12075×100=160 cm\text{Probable Full Height} = \frac{120}{75} \times 100 = 160\text{ cm}

Explanation:

Using the formula for full height, we divide the current height by the percentage of growth completed at that specific age and multiply by 100100 to predict the final adult height.

Problem 2:

Identify the hormone responsible for the following changes: (a) Deepening of voice in boys, (b) Development of breasts in girls.

Solution:

(a) TestosteroneTestosterone, (b) EstrogenEstrogen

Explanation:

TestosteroneTestosterone is the primary male sex hormone produced by the testes, while EstrogenEstrogen is the primary female sex hormone produced by the ovaries, both triggered by the Pituitary glandPituitary\ gland.